This PR allows us to use edge overrides with pre-checks. I forgot to account for the --edge flag when developing pre-check probes in TUN-10388. This should allow us to wire this flag in.
DNSResolver will still be injected via RunDialers, and we will take care of initialization in cmd.go. This allows us to keep pre-checks testable and inject mock DNSResolvers when needed.
I thought about overriding `edgediscovery.ResolveEdge` and `edgeDiscovery.StaticEdge` instead of `allregion.EdgeDiscovery` and `allregionResolveAddrs`, respectively. But that would imply changing our existing probe logic to support `Regions` instead of `[][]EdgeAddr`, which would mean more work. Additionally (and perhaps most importantly), using `Regions` would also require us to create new functions to extract a list of edge addresses for our probe tests. I don't think this would go well with the current implementation of `Regions`, as I believe it's intent is to encapsulate the logic around managing addresses per regions. Adding these functions would mean breaking this encapsulation.
Fixing missing TLS settings. While developing the pre-check probes, I forgot to add the certificate settings, which are essential for establishing a connection to origintunneld. I discovered this while testing cloudflared locally.
This introduces the main precheck logic. This will follow concurrency model, timeout handling, and retry logic established in the SPEC. We will follow the decision flow in the [connectivity pre-checks SPEC](https://wiki.cfdata.org/spaces/TUN/pages/1374967685/Connectivity+Pre-checks+for+cloudflared). You can find an attached image of what the decision flow should look like.
{width=900 height=235}
This PR implements all the dialers and resolvers needed to make pre-checks happen. So this task focuses on the following:
1. Implement the DNS probe: call DNSResolver.Resolve(region)
2. Implement the QUIC probe: call QUICDialer.DialQuic (handshake only, no stream opened) and record the result.
3. Implement the HTTP/2 probe: call TCPDialer.DialEdge (TCP + TLS handshake only, no frames sent) and record the result.
4. Implement the Management API probe: call ManagementDialer.DialContext to api.cloudflare.com:443 and record the result.
5. Export edgeDiscovery as EdgeDiscovery in edgediscovery/allregions/discovery.go so the pre-check can reuse the production DNS path.
This sets up the main components to implement the checker.
Switching `SuggestedProtocol` to a pointer, so we can pass nil whenever both QUIC and HTTP2 fail. We should not be suggesting anything when all our protocols have failed.
The goals of this PR are twofold:
## **1. Introduce a new renderer to output to `stdout`**
Implement the table renderer that will be used to report the results to stdout. The renderer should output something similar to this:
```
─── CONNECTIVITY PRE-CHECKS ──────────────────────────────────────────────────
COMPONENT TARGET STATUS DETAILS
DNS Resolution region1.v2.argotunnel.com PASS Resolved successfully
DNS Resolution region2.v2.argotunnel.com PASS Resolved successfully
UDP Connectivity Port 7844 (QUIC) PASS Handshake successful
TCP Connectivity Port 7844 (HTTP/2) PASS TLS handshake successful
Cloudflare API api.cloudflare.com:443 PASS Reachable
SUMMARY: Environment is healthy. cloudflared will use 'quic' as primary protocol.
──────────────────────────────────────────────────────────────────────────────
```
## **2. Add a log-level renderer**
Add support for structured logging to print the table results as logs. Below is an example of how logs should look like:
```
{"level":"info","run_id":"52828729-dfwd-45b3-w12f-727cbdb4cbd4", "component":"DNS Resolution","target":"region1.v2.argotunnel.com","status":"pass","details":"Resolved successfully","time":"2024-01-15T10:30:00Z","message":"precheck"}
{"level":"info","run_id":"52828729-dfwd-45b3-w12f-727cbdb4cbd4", "component":"DNS Resolution","target":"region2.v2.argotunnel.com","status":"pass","details":"Resolved successfully","time":"2024-01-15T10:30:00Z","message":"precheck"}
{"level":"info","run_id":"52828729-dfwd-45b3-w12f-727cbdb4cbd4", "component":"QUIC Connectivity","target":"Port 7844 (QUIC)","status":"pass","details":"Handshake successful","time":"2024-01-15T10:30:01Z","message":"precheck"}
{"level":"info","run_id":"52828729-dfwd-45b3-w12f-727cbdb4cbd4", "component":"HTTP/2 Connectivity","target":"Port 7844 (HTTP/2)","status":"pass","details":"TLS handshake successful","time":"2024-01-15T10:30:01Z","message":"precheck"}
{"level":"info","run_id":"52828729-dfwd-45b3-w12f-727cbdb4cbd4", "component":"Management API","target":"api.cloudflare.com:443","status":"pass","details":"Reachable","time":"2024-01-15T10:30:01Z","message":"precheck"}
{"level":"info","run_id":"52828729-dfwd-45b3-w12f-727cbdb4cbd4", "hard_fail":false,"suggested_protocol":"quic","time":"2024-01-15T10:30:01Z","message":"precheck complete"}
```
This adds the foundation for the new cloudflared pre-checks by creating a new prechecks package. This adds the following:
* types.go: Status, CheckResult, Report, Config (add IPVersion allregions.ConfigIPVersion field to Config)
* interfaces.go: DNSResolver, TCPDialer, QUICDialer, ManagementDialer
